Why are the results of magnesium content determination by EDTA volumetric method always low?
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Our laboratory is engaged in testing the composition of ores. In the past, the results obtained using magnesium oxide reference samples (national standard samples) were quite good, but recently the results have been consistently on the low side. Could any expert help analyze the reason for this? The method steps remain unchanged; only some of the reagent manufacturers have changed, and the manufacturers of the old reagents no longer exist. Yet even with new reagents, the results are still not satisfactory.
This post was last edited by limingshuguang on 2009-5-4 at 16:33. There is a similar document; you should take a look at it. Reasons for low lead determination values using EDTA titration in high-silica lead ore and methods for improvement The cause of distortion in the measurement data obtained through EDTA titration of lead in silicon-lead ore samples and ways to correct this issue
The situation is different, but I still thank you
What method is being used? Please give a brief introduction so that I can provide a better analysis.
What reagent has changed? Do you have samples from before? Take them out and compare; maybe the content in the sample itself is low
If the EDTA concentration is left at that level for an extended period, it will increase; please mark this
Do you produce lightly calcined powder? Is it related to the type of ore used? Do you determine the total magnesium content? Use hydrochloric acid for sample dissolution – see if there is a significant difference in the amounts
Is the approach suggested by the original poster appropriate? 1. Prepare standard samples and use them to verify the results. 2. Consider the suggestions from various users, identify the relevant influencing factors, and then examine them one by one – issues such as indicators, standard titration solutions, and the calibration of burettes. Only in this way can the causes be identified and ultimately resolved
Is the pH value too low? Generally, titration is carried out under alkaline conditions
If it’s an EDTA standard solution that has been in use for a long time, it may be necessary to calibrate it using CaCO3. Alternatively, there could be an issue with the indicator; you can try preparing a new solution and see